My early morning post on today's Quinnipiac University poll compared Attorney General Richard Blumenthal's past poll numbers with his current showing.
But I failed to make an important distinction: This morning's survey included likely voters, while past Q polls included registered voters. They are, according to Q poll Director Doug Schwartz, apples and oranges.
"Previous polls were all registered voters and traditionally after Labor Day is when the campaign begins. Quinnipiac in all of our states typically will shift from looking at all registered voters to the ones who we call are likely to vote,'' Schwartz said.
UPDATE: Nate Silver of the excellent FiveThirtyEight blog on the New York Times site explains the difference here.
Does it matter? "There is an abundance of evidence this cycle that likely voter polls are more favorable to Republicans than registered voter ones -- a reflection of the superior enthusiasm among their voters this year. And that's great news for Republicans, because likely voter polls are generally more reliable, especially in midterm elections,'' Silver writes.
What makes a likely voter? It's based on vote intention, the people who say they intend to vote, as well as their interest in politics, Schwartz said. "People who are highly interested in politics are more likely to vote on Election Day so we believe this is the best estimate of where the race stands right now."
In other words, comparisons to previous polls of registered voters are pointless.